In a medium saucepan, combine the remaining unsalted butter, sugar, and cane syrup over medium-high heat. Bring mixture to a boil, stirring constantly. Remove from heat and stir in baking soda. Pour hot mixture evenly over both baking sheets of popcorn and nuts. Using a lightly greased spatula, stir the mixture well so that everything is evenly coated.

Bake for about 1 hour, stirring occasionally. Remove caramel corn from the baking sheets and cool completely on waxed paper. Store in an air-tight container for up to 1 week.